Pylons is a Python “glue” web framework, focused around combining several “best of breed” libraries together in a single integrated package. By default, it uses Mako for templates, SQLAlchemy for ORM, Routes for request dispatching, setuptools for deployment, and Beaker for sessions. It's also possible to switch in other components as desired.

• BitTorrent.com was built on Pylons. Performance was decent, and we were reasonably satisfied with the framework.

• Because every Pylons controller is a WSGI app and WSGI requires that functions have a specific signature, information is passed between them through global variables. However, a naive global wouldn't be threadsafe, and so Pylons uses “stacked object proxies” for the c, g, session, req, etc. variables. This makes it very difficult to inspect the Pylons request state through dir(), vars(), or other Python debugging tools.

• Django
• web.py
• TurboGears
• Rails